Well, the second is simply an adaptation of an early baroque piece — a very recognisable one, to wit — into a different tuning. What makes it unusual is that said tuning is based not in octaves, but in tritaves (octave-and-a-fifths), with the timbre of the instruments altered to permit more consonant harmony.
The first, however, is an original sonata using quarter-tone harmony, which is jarring because it is simultaneously familiar and unfamiliar — what constitutes consonance and dissonance is thrown totally out of whack. Furthermore, it uses the natural timbre and overtones of the instrument, meaning that said dissonances are, well, dissonant
. And weird
When all is said and done, I prefer the first piece, but only because I've become accustomed to that kind of weirdness; were I going into this as someone new, I'd probably be more inclined towards the latter.